The present invention relates to a movie screen or the like, and the production of the screen.
It has been long known that grooves cut vertically in a screen will cause light incident upon the screen to reflect horizontally in a pattern depending upon the shape of the grooves. This scattering by the grooves determines the reflectivity pattern and therefore, the viewing angle of the screen. It would, of course, be much more efficient to reflect the incident light rays in a vertical as well as a horizontal pattern. To this end, the prior art has coated the surface of the screen with a diffusing material that will cause sufficient vertical spread of the reflected light rays. The disadvantage, however, of these screens is the complete reliance of these diffusing materials which are highly inefficient as a light-spreading medium and which completely eliminates any screen's ability to reject ambient light falling on the screen outside its viewing area with a resulting serious loss of image contrast.
There have been attempts to free the screen designer from this unwanted dependence on diffusing materials. For example, U.S. Pat. Nos. 2,804,801 and 2,984,152 seek to avoid the use of diffusing materials by designing a screen having three-dimensionally protruding surfaces which reflect the incident light in the desired directions. However, the problem with these screens is that the protruding surfaces are extremely vulnerable to abrasion since their active reflecting surfaces extend outwardly from the screen to such a large degree. Therefore, the simple handling of these screens will result in the deterioration of their light reflecting qualities. Also, such protruding surfaces have not proven practical to manufacture with sufficient uniformity to be acceptable for use as a high brightness screen.